This study seeks to test the hypothesis that a high glycemic diet, by causing reactive hypoglycemia, excessive calorie consumption, and decreased fat oxidation may predispose to obesity. The investigators propose to examine the effects of high- and low-glycemic index meals on hormonal response, energy metabolism and appetite in obese, adolescent boys. The prevalence of significant obesity in the United States, if defined as greater than 120% ideal body weight, ranges from 33% overall to 50% in some minority groups. About 20% of the pediatric population is considered overweight, a figure which has increased by half from 1963 to 1991. Obesity may constitute the most common health problem in America. Associated morbidity includes cardiovascular disease, stroke, diabetes mellitus, cancer, musculoskeletal disorders, pulmonary disease, exercise intolerance, and psychosocial problems. Morbid obesity may confer a mortality rate of over twice that of the general population. Research into the pathophysiology and treatment of obesity assumes great importance to national health.